The research described in this proposal is designed to analyze specific aspects of hormonal control of the central nervous system (CNS) and peripheral targets organs. A terrestrial mollusk has been chosen as a model system which provides the unique opportunity of simultaneously analyzing the CNS and both adult and embryonic cardiovascular systems. The research is designed to test the following hypothesis "Small cardioactive peptide (SCP) hormone and related peptides are multi- functional neurohormones that integrate changes in he responsiveness of cardiovascular function." Three specific aims are: 1) Localize regions of peptide responsiveness in adult heart and major vessels. 2) Localize the CNS cardioregulatory neural network. 3) Describe the development of hormonal responsiveness in the embryonic heart and accessory pump systems. Immunohistochemical localization of SCP will be done using a monoclonal antibody against the peptide. In both adult and developing heart, hormone responsiveness will be localized by ejecting pulses of SCP via a microelectrode at specified regions of the heart. A cellular level analysis of both the heart and the neural network will be done utilizing microelectrode recording that will allow a study of the responsiveness of identified central neurons and the heart. The search for additional elements and latent e peptides in the cardioregulatory network will be continued. A concentration dependence survey will be done with embryos throughout development. The developmental onset of responsiveness will be analyzed by using videomicroscopy to record the cardiovascular responsiveness of embryos to hormones. In addition, localization of hormone responsiveness will be done, as described above, by topical ejection of hormone across the surface of the embryonic heart and cephalopedal pumping system. The interrelated aspects of this project will each provide a survey of hormones responsiveness and details of the time course of action. The cellular level analysis will provide details of the specific actions of hormones on both central neurones and heart muscle. In many human disease states hormonal changes affect both emotions and bodily functions. Little is known regarding the actions of such multifunctional hormones. The results of the proposed research will provide additional knowledge regarding the basic function of hormones. For this reasons the present behavioral and physiological study is highly justified.